Electrochemically actuated firing mechanism



April 10, 1956 Q s-r ETAL 2,741,182

ELECTROCHEMICALLY ACTUATED FIRING MECHANISM Filed Aug. 25, 1954lNl/E/VTOR5 [3111:1101 E5 L. Fun 5'':

Lead-1E 11 Me GI'VELW ATTOENEYS ELECTROCIEMICALLY ACTUATED FlRINGMECHANISM Charles L. Faust and Leslie D. McGraw, Columbus, Git-lo,assignors, by mesne assignments, to the United of America as representedby the Secretary of the Army Application August 25, 1954, Serial No.452,232 2 Claims. (Cl. 102-702) This invention relates to a variabledelay fuze wherein the rate of erosion or decomposition of the anode ofan electrolytic cell is utilized and varied to provide the re quiredpredetermined time between arming and initiation of the fuze.

It is the principal object to provide a device of the nature aforesaidwhich is capable of actuation over a wide range of times, which ispositive and reliable in operation and capable of a wide range ofconditions of use.

Another object of the invention is to provide a device wherein thefiring mechanism is restrained by the tensioned anode of an electrolyticcell and released after the anode has been eroded to the breaking pointby electrolytic action in the cell.

A further object of the invention is to provide means to compensate forchanges in electrolytic action otherwise caused by variation intemperature of the electrolyte.

Other objects and advantages will be apparent from the followingdetailed description and the accompanying drawings in which:

Figure 1 is a schematic view showing the invention in use to release aspring pressed firing pin.

Figure 2 is a similar view showing the invention in use to close acircuit to an electric detonating cap, and

Figure 3 is a sectional view of modified type of electrolytic cell anddetonator means.

Referring now to the drawings 5 identifies an electrolytic cell. Thecell is in the form of a vessel 6 containing an electrolytic solution 7and is closed at its bottom by an acid resistant dielectric seal 8.

The side wall 9 or a portion thereof, is formed of suitable metal suchas copper, to serve as the cathode of the cell. Centrally of the vessel6 and extending through the seal 8 is an elongated rod 10 which issuspended at its upper end as at 11 from a support 12. The rod serves asthe anode of the cell and is formed of a metal such as copper and isshielded by dielectric sleeves 13 and 14 longitudinally spaced thereonto expose a limited portion of its length 15 to the electrolyte 7.

Electrically connected in series with the cell 5 is a source of D. C.voltage 16 whose positive and negative terminals are connected to theanode 10 and the cathode 9, respectively. Electrically connected inseries in the circuit are two variable resistors 17 and 18. With anelectrolyte composition and proportions, such as the one identifiedinfra, the resistor 17 can be set to cause decomposition of the anode tothe breaking point in a predetermined time interval and under apredetermined tension. The resistor 18 will be calibrated in degrees oftemperature and is set to the ambient temperature reading to compensatefor the known difference in electrolytic decomposition etiected by aspecified electrolyte and current density at the temperatures for whichthe resistor is calibrated.

In Figure 1 the rod 10 which serves as the anode of the cell 5, iselongated beyond the cell and has a firing pin 19 secured to its end. Anabutment 20 is secured near the firing pin and receives the end thrustof a helical spring 2,741,182 enemas Apr. 10, 1956,

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21 which surrounds the rod 10 between the abutment and a shoulder 22 onthe firing pin 19. When the rod is weakened by the erosion of anode 10to the breaking point under the tension of spring 21, the latter drivesthe firing pin 19 into a percussion cap 23 and detonates an explosivecharge 24.

in Figure the rod 10 is secured to a spring contact member 25 which isurged by its tension toward a second contact member 26 to thereby closea firing circuit when the rod 10 is broken. The circuit extends from thebattery 16 to an electrically fired squib 27, which in turn detonates anexplosive charge 28. A switch 29, Figures 1 and 2, normally holds thecircuit in open safe position and is manually closed to start the timedelay period.

in Figure 3 a somewhat different assembly of electrolytic cell 5' andfiring means is illustrated. The vessel 6' contains an electrolyticsolution 7' and is closed at its bottom by an acid resistant dielectricseal 8'. A cover 211 formed with the vessel or as a separate part,serves a purpose similar to the abutment 20 of Figure 1. The side wall 9of the cell is formed of suitable metal, such as copper, to serve as thecathode of the cell. A rod 10' formed of a metahsuch as copper, servesas the anode thereof and extends through the cell from the bottom 8'thereof where it is secured, a portion 15'. of the rod being immersed inthe electrolyte. The rod 10' extends through cover 26' to carry a firingpin 19'. Mounted upon the cover 20' and insulated therefrom by a washer32 of dielectric material is a metal washer 335 which is in electricalcontact with the rod 10 and included in a circuit, with the side wall 9of the cell 5, similar to the circuit shown in Figure 1. The rod 10'extendswith a sliding fit through apertures in the washers 32 and 33.

A helical spring 34 surrounds the rod and is confined between the metalwasher 33 and the firing pin 19'. When the rod 10 is weakened to thebreaking point by electrolytic erosion at the point 15' the tension ofspring 34 causes breakage thereof and drives the firing pin 19' into apercussion cap 23' to detonate an explosive charge 24".

in one form of the invention successfully operated an electrolyte madeup the proportions of 150 grams per liter of CuSOrSl-IzO plus 50 gramsper liter of H2504 of specific gravity 1.84 was used. Wires or rods 10of copper of initial diameter of 0.0355 to .0370 inch were used. When acurrent of .006 amp. was used at about F. a time delay of approximately3 hours was obtained. Since, without temperature compensation, the timedelay will decrease with increase in ambient temperatures, the re.sister 18 will he graduated so as to result in decreased current withincrease in ambient temperature. By various.

combinations of electrolyte, wire diameter current density and springtension, the range of time delays possible with the invention may bewidely varied to suit any desired or required conditions of use. In theexample given, the final diameter of the wire 10, at breakage, was about0.025".

The operation of the invention is as follows:

When it is desired to fire an explosive charge of a type shown in Figure1 of the drawings, variable'res'istor 17 is set in accordance with apredetermined time delay. The variable resistor 18 is set to registerwith calibrations thereon (not shown) corresponding to ambienttemperature. The fuze is armed by closure of switch 29. Current thenflows from the portion 15 of the rod 10 through the electrolyte 7 to theside wall 9 to thereby eliect anodic dissolution of the rod and finallyweakening it to the breaking point under tension of springs 21, 25 or34. The.

firing pin 19 on the end of rod 10 is then driven by its. spring 21 intothe percussion cap 23 to explode the charge 24, Figure 1.

The operation of the form of the invention shown in Figure 2 isidentical excepting the addition of a parallel 3 ircuit, throughcontacts 25 and 26, connecting the battery 6 with the electrically firedsquib 27. When the rod 10 1 Figure 2 breaks the spring contact member 25moves 3 close the circuit 30 through the fixed contact member 6 to thebattery 16 and squib 27 to detonate the exploive charge 28.

The operation of the form of the invention shown in igure 3 is similarto the operation of Figure 1. The ele- .ients of the cell 5 and thefiring means are rearranged 3 illustrate another form of the inventionbut in this form, he spring 34 is not required to overcome anyfrictional esistance between the rod and bottom of the cell.

While we have disclosed three forms of the invention resently preferredby us, various changes and modificaions will occur to those skilled inthe art after a study if the present disclosure. Hence the disclosure isto be aken in an illustrative rather than a limiting sense; and t is ourdesire and intention to reserve all modifications alling Within thescope of the subjoined claims.

'Having now fully disclosed the invention what we .laim and desire tosecure by Letters Patent is:

l. A time delay mechanism comprising a vessel having x metallic wall, anelectrolyte therein, a metallic rod subect to decomposition in saidelectrolyte, a source of elec- :ric energy in a circuit connecting themetallic wall and 70d to effect electrolytic decomposition of themetallic :od within the vessel, a first variable resistor means in :hecircuit to control the time of decomposition of the metallic rod, and asecond variable resistor means in said circuit to compensate foractivity changes in the electrolyte due to ambient temperature changes.

2. In a time delay fuze, an electrolytic cell including a container foran electrolyte, an anode comprising a metallic wire fixed at one end andextending through said container, spring means connected with the otherend of said wire to tension the same, circuit means including said celland anode to dissolve the latter to the breaking point under urge ofsaid spring means, a primer, means no to position initiating saidprimer, said means being restrained in safe position by said anode untilbroken, said circuit means including aiirst variable resistor settableto determine the delay period of said fuze, and a second variableresistor settable to correct for variations in time delay otherwisecaused by variations ambient temperature.

References Cited in the file of this patent UNITED STATES PATENTS1,558,784 Bleecker Oct. 27, 1925 2,314,678 Zint Mar. 23, 1943 2,398,266Whitesell, Ir. Apr. 9, 1946 2,526,670 Kissinger et al. Oct. 24, 1950FOREIGN PATENTS 336,844 Great Britain Oct. 23, 1930

1. A TIME DELAY MECHANISM COMPRISING A VESSEL HAVING A METALLIC WALL, ANELECTROLYTE THEREIN, A METALLIC ROD SUBJECT TO DECOMPOSITION IN SAIDELECTROLYTE, A SOURCE OF ELECTRIC ENERGY IN A CIRCUIT CONNECTING THEMETALLIC WALL AND ROD TO EFFECT ELECTROLYTIC DECOMPOSITION OF THEMETALLIC ROD WITHIN THE VESSEL, A FIRST VARIABLE RESISTOR MEANS IN THECIRCUIT TO CONTROL THE TIME OF DECOMPOSITION OF THE METALLIC ROD, AND ASECOND VARIABLE RESISTOR MEANS IN SAID CIRCUIT TO COMPENSATE FORACTIVITY CHANGES IN THE ELECTROLYTE DUE TO AMBIENT TEMPERATURE CHANGES.